yading@10: @chapter Bitstream Filters
yading@10: @c man begin BITSTREAM FILTERS
yading@10: 
yading@10: When you configure your FFmpeg build, all the supported bitstream
yading@10: filters are enabled by default. You can list all available ones using
yading@10: the configure option @code{--list-bsfs}.
yading@10: 
yading@10: You can disable all the bitstream filters using the configure option
yading@10: @code{--disable-bsfs}, and selectively enable any bitstream filter using
yading@10: the option @code{--enable-bsf=BSF}, or you can disable a particular
yading@10: bitstream filter using the option @code{--disable-bsf=BSF}.
yading@10: 
yading@10: The option @code{-bsfs} of the ff* tools will display the list of
yading@10: all the supported bitstream filters included in your build.
yading@10: 
yading@10: Below is a description of the currently available bitstream filters.
yading@10: 
yading@10: @section aac_adtstoasc
yading@10: 
yading@10: @section chomp
yading@10: 
yading@10: @section dump_extradata
yading@10: 
yading@10: @section h264_mp4toannexb
yading@10: 
yading@10: Convert an H.264 bitstream from length prefixed mode to start code
yading@10: prefixed mode (as defined in the Annex B of the ITU-T H.264
yading@10: specification).
yading@10: 
yading@10: This is required by some streaming formats, typically the MPEG-2
yading@10: transport stream format ("mpegts").
yading@10: 
yading@10: For example to remux an MP4 file containing an H.264 stream to mpegts
yading@10: format with @command{ffmpeg}, you can use the command:
yading@10: 
yading@10: @example
yading@10: ffmpeg -i INPUT.mp4 -codec copy -bsf:v h264_mp4toannexb OUTPUT.ts
yading@10: @end example
yading@10: 
yading@10: @section imx_dump_header
yading@10: 
yading@10: @section mjpeg2jpeg
yading@10: 
yading@10: Convert MJPEG/AVI1 packets to full JPEG/JFIF packets.
yading@10: 
yading@10: MJPEG is a video codec wherein each video frame is essentially a
yading@10: JPEG image. The individual frames can be extracted without loss,
yading@10: e.g. by
yading@10: 
yading@10: @example
yading@10: ffmpeg -i ../some_mjpeg.avi -c:v copy frames_%d.jpg
yading@10: @end example
yading@10: 
yading@10: Unfortunately, these chunks are incomplete JPEG images, because
yading@10: they lack the DHT segment required for decoding. Quoting from
yading@10: @url{http://www.digitalpreservation.gov/formats/fdd/fdd000063.shtml}:
yading@10: 
yading@10: Avery Lee, writing in the rec.video.desktop newsgroup in 2001,
yading@10: commented that "MJPEG, or at least the MJPEG in AVIs having the
yading@10: MJPG fourcc, is restricted JPEG with a fixed -- and *omitted* --
yading@10: Huffman table. The JPEG must be YCbCr colorspace, it must be 4:2:2,
yading@10: and it must use basic Huffman encoding, not arithmetic or
yading@10: progressive. . . . You can indeed extract the MJPEG frames and
yading@10: decode them with a regular JPEG decoder, but you have to prepend
yading@10: the DHT segment to them, or else the decoder won't have any idea
yading@10: how to decompress the data. The exact table necessary is given in
yading@10: the OpenDML spec."
yading@10: 
yading@10: This bitstream filter patches the header of frames extracted from an MJPEG
yading@10: stream (carrying the AVI1 header ID and lacking a DHT segment) to
yading@10: produce fully qualified JPEG images.
yading@10: 
yading@10: @example
yading@10: ffmpeg -i mjpeg-movie.avi -c:v copy -bsf:v mjpeg2jpeg frame_%d.jpg
yading@10: exiftran -i -9 frame*.jpg
yading@10: ffmpeg -i frame_%d.jpg -c:v copy rotated.avi
yading@10: @end example
yading@10: 
yading@10: @section mjpega_dump_header
yading@10: 
yading@10: @section movsub
yading@10: 
yading@10: @section mp3_header_compress
yading@10: 
yading@10: @section mp3_header_decompress
yading@10: 
yading@10: @section noise
yading@10: 
yading@10: @section remove_extradata
yading@10: 
yading@10: @c man end BITSTREAM FILTERS